During the time period that comics first became a form of published media, the roll of women in society was much different than it is today. Women today hold very prominent roles in society including the government, celebrities, CEOs of large businesses and corporations, as well as in Police Departments and even the military. If the first edition of Wonder Woman came out today, society would absolutely attack it as a sexist comic that puts down women. This is really only because of the prominent role of women in today's society. Back in the time period of Wonder Woman, women were encouraged to take on the role of the "housewife". It was not something that was looked down upon or that meant women were not fulfilling their potential. It was what was encouraged of women, and what was expected.
There weren't many female super heroes in comic books, Wonder Woman being the most famous and prominent. Some say that because of this comic books are sexist. They say that the writers don't believe that women are capable of what men are, and therefore they don't depict them as heroes and powerful. I disagree with this. The comic book characters are created more for the target demographic. Most comic book readers are males. This is why the overwhelming majority of comic book heroes are males. Its not because women aren't capable of what men are, it has to do with what is going to sell the most comics. The comic book business is after all a business, so the writers have to keep the readers happy.
So are comics inherently sexist? No not on purpose. Sure today the comics of the earlier 20th century may come of as sexist, but at the time they were widely accepted as a legitimate reflection of what the culture was.